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Issue 33, 2018
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Aluminum enhances photochemical charge separation in strontium titanate nanocrystal photocatalysts for overall water splitting

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Abstract

Strontium titanate (SrTiO3) is a well-known photocatalyst for overall water splitting (OWS) under ultra-violet irradiation. Recently, it was shown that Al-doped SrTiO3 microparticles prepared by flux-mediated solid-state reaction catalyze OWS with an apparent quantum efficiency of 30% at 360 nm, the highest value reported so far for strontium titanate. However, the roles of Al3+ and of the particle morphology in controlling the activity are not clear. Here we report a new synthetic route to well defined nanocrystals of Al:SrTiO3 with controllable Al-concentration (3–8 atom%) using TiO2, Sr(OH)2 and Al(NO3)3 as starting materials. X-Ray diffraction and transmission electron microscopy confirm the presence of perovskite-type cubic nanoparticles with size of 60 nm. After loading with a Rh2−yCryO3 cocatalyst, nano-Al:SrTiO3 catalyzes OWS under UV/vis illumination from a Xe lamp. The activity shows a volcano-like dependence on Al concentration, confirming that Al3+ content is a key factor for the activity. Nanocrystals doped with 7.2 atom% Al show the activity of 53 μmol H2 per hour under 240 mW cm−2 UV illumination and an AQE of 0.06% at 375 nm. Based on surface photovoltage spectroscopy (SPS), aluminum enhances photochemical charge separation in the Al:SrTiO3 nanocrystals and reduces electron and hole trapping. However, under UV/vis illumination, the Al:SrTiO3 nanocrystals are found to be 40 times less active than Al:SrTiO3 microparticles made by flux reaction in SrCl2. The lower activity of the nanoparticles is due to optical shielding from the Rh2−yCryO3 co-catalyst.

Graphical abstract: Aluminum enhances photochemical charge separation in strontium titanate nanocrystal photocatalysts for overall water splitting

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Supplementary files

Article information


Submitted
20 Jun 2018
Accepted
01 Aug 2018
First published
01 Aug 2018

J. Mater. Chem. A, 2018,6, 16170-16176
Article type
Paper
Author version available

Aluminum enhances photochemical charge separation in strontium titanate nanocrystal photocatalysts for overall water splitting

Z. Zhao, E. J. Willard, H. Li, Z. Wu, R. H. R. Castro and F. E. Osterloh, J. Mater. Chem. A, 2018, 6, 16170
DOI: 10.1039/C8TA05885G

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